Hopefully, Axew's lack of training is a plot point. With a good/decent payoff.It is true that Dragonite will surely become a powerhouse in Iris' team, but I really don't see how that will stop her from training Axew. If I recall correctly, both Iris and the village elder did state that Iris' goal during this whole journey of hers was indeed to actually train and evolve Axew, making it stronger, and at the same time growing up and mature alongside with it. We all know how weak Axew currently is, considering Iris hasn't done that much, but as Season 2 started it did seem like she started to take its training more seriously, challenging Cynthia of all people, as well as putting up against Excadrill in a sparring match. The Dragon Master goal is just something that Iris is hoping to achieve too while she's training Axew, but having Axew evolve is definitely something I'd say takes priority. I don't think she'll quit training Axew just because she catches Dragonite. Sure, I could see it not evolving until the very end of the series, but I still don't think that she'll drop all her training with Axew just because of Dragonite, as her goal of evolving Axew still won't be completed.